Synthesis and Characterization of ABA Triblock Copolymers Containing Smectic C* Liquid Crystal Side Chains via Ring-Opening Metathesis Polymerization Using a Bimetallic Molybdenum Initiator

Abstract

A series of monomers suitable for ring-opening metathesis polymerization (ROMP) containing a side chain liquid crystal mesogen have been synthesized, where the mesogen is biphenyl-4-carboxylic acid 4-(1-butoxycarbonyl-ethoxy)phenyl ester (abbreviated as BPP4). Two of the monomers have BPP4 attached to norbornene with a 6- or 10-carbon spacer ((R)-4‘-(5-bicyclo[2.2.1]hept-5-en-2-yl-pentyloxy)-BPP4, NB6wBPP4, and (R)-4‘-(10-bicyclo[2.2.1]hept-5-en-2-yl-decyloxy)-BPP4, NB10wBPP4, respectively), and the third monomer has BPP4 attached to norbornadiene via a 10-carbon spacer ((R)-4‘-(10-bicyclo[2.2.1]hepta-2,5-dien-2-yl-decyloxy)-BPP4, NBD10wBPP4). The monomers were polymerized by ROMP using the bimetallic initiator, {Mo(NAr)(ORF6)2[=CHC5H4]}2Fe (Ar = 2,6-diisopropylphenyl, ORF6 = OCMe(CF3)2). ABA triblock copolymers were also synthesized where the B = NBD10wBPP4 or NBnwBPP4 (n = 6, 10) and A = methyltetracyclododecene (MTD). All polymerizations are living with isolated yields greater than 90% and polydispersi...